Cassava varietal improvement in Vietnam
In recent years (1990-1995) the cassava area in Vietnam has remained stable, or has increased slightly in the south due to the new demand for cassava roots used for starch processing. Therefore, our cassava breeding program, in collaboration with CIAT, has put a high priority on developing new varieties with high yield potential and high dry matter and starch content in the roots.
Due to the particular agro-climatic conditions in Vietnam the country can be divided into two large regions. The south is characterized by a tropical climate, while the north has a subtropical climate. So, new varieties adapted to these specific environments are also needed.
Out of the 29 promising clones introduced from the Thai-CIAT program in 1989 and 1990, two best selections, KM60 and KM94, have been giving 17 to 112% higher dry root yields and 10 to 103% higher fresh root yields compared to the local cultivars at research stations, and 30 to 47% higher fresh root yields in cassava production zones. Both KM60 and KM94 were officially released early in 1995. They were grown over 7000 ha in 1995 and are expected to be planted in about 30,000 ha in the 1996/97 crop year. The additional economic benefit resulting from adoption of the new cultivars was estimated to have reached 0.95 million US dollars in 1995 and is expected to reach 5 million US dollars in 1996.
Some promising clones may be adapted to specific locations. Clone SM937-26 gave very good yields at Lam Dong and Khanh Hoa provinces, CMR29-60-15 and SMI 157-3 in Ha Tay province, while SMI 157-3 and SM981-3 were best in Bac Thai province. These clones are now included in Regional Trials and in the On-farm Evaluation Network in 1996.
Follow-up selection of genotypes adapted to our cassava production conditions started in 1990. Some promising clones, like OMR33-17-15 in the south and CM4955-7 in the north, are being evaluated on farmer's fields this year. They are both the result of intensive selection by HARC and the Agro-forestry College in Bac Thai from hybrid seeds provided by CIAT/Colombia and the Thai-CIAT program. Although the rate of selection with CIAT/Colombia materials is not quite as high as those from the Thai-CIAT program, the greater genetic diversity of this material is playing an important role in cassava breeding and genetic improvement in Vietnam. Results from our current selection will identify new high-yielding cultivars and bring economic benefits for growers and processors; they may also open up new export opportunities by greater product competitiveness in international markets.